Currently, approximately 100 MW is being transmitted through the cable for testing purposes, but a fault occurred causing an unexpected transmission of 1400 MW for a short period of time. The incident lasted less than a minute, starting from 09.11 AM on 10 September. This affected the system frequency, resulting in 0,5Hz change in the Nordic power grid. The incident caused automatic adjustment of the power on two interconnectors in the Nordic region, Swepol between Sweden and Poland and Konti-Scan between Sweden and Denmark. Gas turbine production was also automatically started in Sweden. In addition, the incident led Equinor's refinery at Melkøya to switch to island mode operation, and a Finnish power plant stopped production for a short period of time.  

- These are faults we do not want to experience, and we regret that this affected the Nordic synchronous area. Fortunately, we have good measures in place to deal with such frequency changes and the fault did not pose a threat to the general supply of electricity. The routines worked well, says Gunnar Løvås, EVP for Market and System Operation in Statnett.  

- The incident also shows how important it is to carry out thorough tests of such a connection before it is put into operation and becomes part of the power system. We are finalizing two large interconnectors to Germany and England respectively. It is necessary to see how they affect the system before they are fully phased in, says Løvås.  

Investigations are underway to identify the cause of the incidentPreliminary investigations indicate that a malfunction in the interconnector's local operation system software may have caused the incident. There is no reason to suspect damage to the interconnector itself. Testing of the interconnector will continue until December this year, before NordLink is put into full trial operation. Ordinary operations start next year.  

The NordLink project is owned 50% by Norwegian TSO Statnett and 50% by the German partners TenneT and KfW. The international connection will have a capacity of 1,400 MW and runs between Tonstad in Sirdal in Norway and Wilster in Schleswig-Holstein in Germany. The total investment cost for the project is 1.5 - 2 billion euros.